Eccentric bolt for attaching mission pod to aircraft

This non-provisional patent application claims priority to U.S. Provisional Patent Application No. 63/141,437 filed on Jan. 25, 2021, which is incorporated by reference as if fully provided herein.

The disclosure relates to the field of fasteners, and in particular, to an eccentric bolt.

Some aircraft, such as military aircraft, may be equipped with so-called mission pods that detachably secure to an external surface of the aircraft. The pods may house various components or payload that facilitate execution of various operations. For example, a pod may carry electronics for mission-specific communications or surveillance. It is generally beneficial for the pods to be easily swapped on the aircraft for mission adaptability. Additionally, it is beneficial for the pods to attach with different aircraft in a manner that is secure and aligned despite manufacturing tolerance differences among aircraft.

Embodiments described herein use an eccentric bolt for attaching a mission pod to an aircraft. The eccentric bolt is inserted through a joint, such as a clevis and lug fitting, that attaches a mission pod with the external surface of the aircraft. Due to manufacturing tolerances of the aircraft, two joints of the aircraft for attaching a pod may be slightly misaligned. The eccentric bolt advantageously enables fine adjustment in one of the joints to correct or compensate for the misalignment between the aircraft and the pod mounting fittings. Moreover, the eccentric bolt facilitates quick, secure attachment of the mission pod to the aircraft in a compact size without drilling.

One embodiment is an eccentric bolt to secure a clevis and lug fitting. The eccentric bolt includes a head and a shank. The shank includes multiple shank sections that successively decrease in diameter in an axial direction from the head toward a tail end of the shank. One of the shank sections is an eccentric shank section that is off-center with respect to a center axis of the shank. The eccentric shank section is configured to engage the lug prior to engagement of concentric shank sections with the clevis. While the eccentric shank section is engaged with the lug, the shank is configured to rotate to align the concentric shank sections with the clevis, and to insert through the clevis and lug fitting to compensate for misalignment of the clevis and lug fitting.

A further embodiment is a method of attaching a first structure having a clevis to a second structure having a lug. The method includes positioning the lug between forks of the clevis to approximately align respective holes in an axial direction to form a clevis and lug fitting, and inserting an eccentric bolt partially through the clevis and lug fitting until an eccentric shank section of the eccentric bolt engages the lug. The method also includes rotating the eccentric bolt to compensate for horizontal misalignment of the clevis and lug fitting, and adjusting the clevis vertically to compensate for vertical misalignment of the clevis and lug fitting. The method further includes inserting the eccentric bolt further through the clevis and lug fitting to engage the clevis with the eccentric bolt and attach the first structure with the second structure.

A further embodiment is a method of attaching a mission pod with an aircraft. The method includes attaching a first end of the mission pod to the aircraft by installing a first straight bolt through a first joint, and attaching a second end of the mission pod to the aircraft by installing a second straight bolt through a second joint. The method also includes attaching the first end of the mission pod to the aircraft by installing an eccentric bolt through a third joint to compensate for misalignment between the first joint and the third joint.

Other example embodiments may be described below. The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings.

The figures and the following description illustrate specific exemplary embodiments of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within the scope of the disclosure. Furthermore, any examples described herein are intended to aid in understanding the principles of the disclosure, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the disclosure is not limited to the specific embodiments or examples described below, but by the claims and their equivalents.

is a front view of an aircraft. The aircraftincludes a fuselage, wings, horizontal stabilizers, and a vertical stabilizer. A lower surfaceof the fuselageincludes a mission podattached to its external surface. The mission podmay house various components or payload that facilitate execution of various operations. For example, the mission podmay carry weapons or electronics (e.g., communications or surveillance equipment) for mission-specific operations. The mission podis detachable from the aircraftfor mission adaptability. Although one attachment site is shown in, it will be appreciated that the aircraftmay include alternative or multiple attachment locations on aircraftfor swapping mission podson the external body of the aircraft.

is a front perspective view of the mission podattached to an external bodyof the aircraftvia one or more joints. In particular, the jointsmay comprise clevis and lug fittings. The clevisis a component or structure of the mission podand includes a yoke structure, or forks, with a concentrically aligned pair of holes. The lugis a component or structure of the aircraftand includes a projecting piece with a hole that is configured to situate between the pair of holes of the clevis. Thus, the mission podmay be detachably coupled with the aircraftby installing a boltthrough the aligned holes of the clevisand lug. In this example, a front end of the mission podis attached with two joints, or two clevis and lug fittings, disposed at a left side and right side.

Unfortunately, manufacturing tolerances of the aircraftmay sometimes result in slight misalignment of left/right lugs. Similarly, slight manufacturing variation of a mission podmay introduce slight misalignment between left/right devises. Accordingly, after coupling one clevisand lugvia bolt(e.g., at right side) to establish a joint axis, the other clevisand lug(e.g., at left side) may be undesirably offset with respect to each other and the joint axis. For this reason, jointsare sometimes match drilled or fitted with complex link assemblies. However, match drilling is time consuming and necessitates coordinated tooling and drilling that is not compatible with easily swapping mission pods. Match drilling also eliminates interchangeability of mission pods since their attachment becomes limited to the aircraft and specific attachment location to which it has been match drilled. Link assemblies add complexity to installing and removing mission podsand are only able to transmit loads in a single vector along the length of the link.

is a perspective view of an eccentric boltin an illustrative embodiment. The eccentric boltis configured to install through a joint to correct misalignment. For example, with reference to, the eccentric boltmay be installed through the clevisand lug(e.g., at left side) to correct misalignment therein after coupling clevisand lugvia bolt(e.g., at right side). As described in greater detail below, rotation of the eccentric boltas it is inserted through the jointcompensates for misalignment in the joint. Advantageously, the eccentric boltfacilitates quick, secure attachment of the mission podto the aircraftin a compact size without drilling or complex link assemblies. Additionally, the eccentric boltis advantageously configured to react loads in multiple directions perpendicular to the axial direction of the eccentric bolt.

The eccentric boltincludes a headand a shank. The shankincludes multiple shank sections-that successively decrease in diameter in an axial direction from the headtoward a tail end of the shank. One of the shank sections-is an eccentric shank sectionthat is eccentric with respect to a center axisof the shank. The eccentric shank sectionhas an axis of rotationthat is off center with respect to the center axisof the shank. Therefore, as the eccentric boltrotates around the center axisan outer circumferential position of the eccentric shank sectionchanges with respect to the center axis.

In one embodiment, the shank sections-include: an upper shank sectionthat is concentric and has a first diameter, the eccentric shank sectionthat is eccentric and has as second diametersmaller than the first diameter, a lower shank section that is concentric and has a third diametersmaller than the second diameter, and a bottom shank sectionthat is concentric and has a fourth diametersmaller than the third diameter. Moreover, the eccentric shank sectionand its second diameterinclude different distances, dand d, from the center axisof the shankto its outer circumference. In other words, the eccentric shank sectionincludes an offset axis from the center axis. Accordingly, the eccentric shank sectionoccupies a different offset area as the eccentric boltis rotated about the center axis. Additionally, the shankincludes multiple ramps-to taper the diameter between adjacent ones of the shank sections-. The eccentric shank sectionis thus configured to compensate for misalignment in a joint as described in greater detail below.

is a side cross-sectional view of the eccentric boltpartially inserted through a clevis and lug fittingin an illustrative embodiment. The clevis and lug fittingincludes a clevisand a lug. In some embodiments, the clevisis a component or structure of a mission pod (e.g., mission pod) and includes a yoke structure, or forks, with a concentrically aligned pair of holes-. The pair of holes-extend through a respective pair of bushings-situated in the forks, and the first holemay be larger in diameter than the second hole. The lugmay be a component of an aircraft at which an external structure (e.g., mission pod) is detachably coupled. The lugmay include a holethat is configured to situate/align between the pair of holes-of the cleviswith a diameter that is a size between the diameters of the pair of holes-. The holemay include a passage extending through a bearing, such as a spherical ball bearing or plane bearing, of the lugto prevent twisting forces acting upon the lug. Generally, as described in greater detail below, the eccentric boltis configured to engage in a fit through the holes of the clevis and lug fittingto compensate for misalignment.

In situations in which the clevis and lug fittingincludes slight misalignment due to manufacturing tolerances (e.g., the holeof the lugis misaligned with the pair of holes-of the clevis), a regular straight bolt may not correctly align/install unless on-site drilling is performed which typically slows and complicates installation. By contrast, the eccentric boltadvantageously enables fine adjustment in the clevis and lug fittingby rotating as the shank sections-engage corresponding areas of the clevis and lug fitting. In particular, the upper shank sectionis concentric and sized to correspond with a first holeof the clevis, the eccentric shank sectionis eccentric and sized to correspond with the bearingof the lug, the lower shank sectionis concentric and sized to correspond with the second holeof the clevis, and the bottom shank sectionis concentric and may be threaded for securing a nut.

As shown in, the shank sections-are sized such that the eccentric shank sectionis configured to engage the bearingof the lugbefore the upper shank sectionengages the first holeof the clevisand before the lower shank sectionengages the second holeof the clevis. This advantageously provides a benefit in that, with the eccentric shank sectionengaged before the upper shank sectionand the lower shank section, the eccentric shank sectionis configured to secure a centerline of the lugto enable vertical adjustment of the cleviswith respect to the lug, and to enable rotation of the eccentric boltuntil the eccentric boltfits through the clevis and lug fittingto compensate for the misalignment.

Additionally, the eccentric boltincludes multiple ramps-configured to facilitate alignment of the eccentric boltwith respect to the clevis and lug fittingas the eccentric boltis partially inserted and rotated. One of the ramps-is an eccentric rampthat tapers the diameter between the eccentric shank sectionand the lower shank section. As the eccentric boltis partially inserted through the clevis and lug fitting, slight misalignment of holes of the clevis and lug fittingmay cause the eccentric shank sectionto resist sliding through the lug. The eccentric rampis configured to guide adjustment of the lugwith respect to the clevisso that the eccentric shank sectionslides into the lug. This allows the eccentric boltto be partially inserted into the lugand rotated to aid further insertion as increased alignment is achieved. The multiple ramps-are thus configured to start/improve the insertion of the eccentric boltand indicate which way to rotate the eccentric boltfor self-alignment along with the vertical movement of a mission pod (and its clevis) to achieve alignment.

While the eccentric shank sectionis engaged with the lug, the shankof the eccentric boltis configured to rotate to align the concentric shank sectionsandwith the clevis, and to insert through the clevis and lug fittingto compensate for misalignment of the clevis and lug fitting. The correctly aligned offset of the eccentric shank sectionadvantageously enables the installed eccentric boltto react forces in multiple directions (e.g., a vertical z direction and a horizontal x direction) perpendicular to the axial direction (e.g., y direction) of the eccentric bolt. The eccentric boltthus facilitates quick, secure attachment of an external structure (e.g., mission pod) to an aircraft in a compact size without drilling. It will be appreciated, however, that the eccentric boltmay be adapted or applied to alternative applications or types of joints.

is a flow chart illustrating a methodof attaching a first structure having a clevis to a second structure having a lug in an illustrative embodiment. The steps of methodwill be described with respect to the eccentric boltand clevis and lug fittingof, although one skilled in the art will understand that the methods described herein may be applied to alternative configurations of joints and bolts. The steps of the methods described herein are not all inclusive and may include other steps not shown. The steps for the flow charts shown herein may also be performed in an alternative order.

In step, the lugis positioned between forksof the clevisto approximately align respective holes (e.g., approximately align holewith holes-) in an axial direction to form a clevis and lug fitting. As earlier described, in some embodiments, the clevisbelongs to the first structure or external structure such as a mission pod that is to be assembled or coupled with the lugof a second structure such as an aircraft.

In step, the eccentric boltis partially inserted through the clevis and lug fittinguntil an eccentric shank sectionof the eccentric boltengages the lug. For example, in one embodiment, the eccentric boltis partially inserted through the clevis and lug fittinguntil the eccentric rampengages the lugand resists sliding through the lugdue to misalignment of the respective holes of the clevisand the lug. In optional step, the lugis engaged with the eccentric shank sectionbefore engaging the cleviswith concentric shank sections (e.g., upper shank sectionand lower shank section) of the eccentric bolt.

In step, the eccentric boltis rotated to compensate for horizontal misalignment of the clevis and lug fitting. In step, the clevisis adjusted vertically to compensate for vertical misalignment of the clevis and lug fitting. For example, the entire mission pod may be moved vertically as a rigid body including the clevisto adjust vertical misalignment of the pod clevis and aircraft lug. In step, the eccentric boltis inserted further through the clevis and lug fittingto engage the cleviswith the eccentric boltand attach the first structure with the second structure. This enables optional stepof installing a keeper on the eccentric boltto prevent the eccentric boltfrom rotating, and optional stepof reacting loads with the eccentric boltin a vertical direction perpendicular to the axial direction of the eccentric bolt, and also in a horizontal direction perpendicular to the axial direction of the eccentric bolt. That is, a keeper positioned on the headlocks the eccentric boltin the aligned position so that load can be reacted instead of allowing the eccentric boltto rotate in the joint. Methodthus provides a benefit in enabling quick, secure attachment of the first structure to the second structure as compared to prior techniques.

In some embodiments, the eccentric boltmay complete installation using an installation nut (e.g., nut). The bottom shank sectionmay include a threaded portion with increased length to sufficiently protrude through the second holeof the clevis, allowing a nut to engage the bottom shank sectionand pull the eccentric boltthrough the clevison installation. For example, the eccentric boltmay be rotated while slightly torquing the installation nut (and/or pushing the eccentric bolt) until the eccentric boltcenters or slides onto/through the clevis. This may continue until the eccentric boltis fully seated. In further embodiments, the eccentric boltmay be prevented from rotating in the joint by installing a keeper on the head. In yet another embodiment, the eccentric boltmay include a hole drilled through the center axisto be used in conjunction with a tool to remove the eccentric boltfrom the clevisduring decoupling.

is a bottom view of a mission podattached with an aircraftin an illustrative embodiment. In particular, the mission podis attached via installations-. Moreover, the installations-may be secured in order of their numerical element (e.g., installationis secured first, installationis secured second, etc.). For example, the installations-may include bolt installations installed in order. After the first installationand the second installationare secured, a line of rotationis established that may cause a misaligned axisbetween the first installationand the third installation. Accordingly, steps as further described inmay be performed to correct the misalignment. After the eccentric boltis aligned and seated in the third installation, a keepermay be installed on the eccentric boltto hold the alignment and allow the third installation to react loads in multiple directions perpendicular to an axial direction of the eccentric bolt. The keepermay engage the headof the eccentric boltprior to nut torque to aid installation of the eccentric bolt.

is a flow chart illustrating a methodof attaching a mission pod with an aircraft in an illustrative embodiment. The steps of methodwill be described with respect to a mission pod and an aircraft, although one skilled in the art will understand that the methods described herein may be applied to one or more alternative structures to be coupled together. The steps of the methods described herein are not all inclusive and may include other steps not shown. The steps for the flow charts shown herein may also be performed in an alternative order.

In step, a first end (e.g., back end) of the mission podis attached to the aircraftby installing a first straight bolt through a first joint (e.g., first installation). In step, a second end (e.g., forward end) of the mission podis attached to the aircraftby installing a second straight bolt through a second joint (e.g., second installation). In step, the first end of the mission podis attached to the aircraftby installing the eccentric boltthrough a third joint (e.g., clevis and lug fitting) to compensate for misalignment between the first joint and the third joint. Stepmay include, for example, the steps of methodearlier described. Accordingly, methodadvantageously enables quick, secure attachment of a mission pod to an aircraft in a manner that compensates for the misaligned axis.

is a graphical illustration of an example joint misalignment corrected by an eccentric boltin an illustrative embodiment. Suppose, for this example, that the eccentric boltincludes an offsetof 0.0300 inches. With reference tofor example, the eccentric shank sectionmay include an axis of rotationthat is offset 0.0300 inches from the center axis. Thus, by using the eccentric boltin a joint, one structure (e.g., mission pod) can be adjusted relative to the other structure (e.g., aircraft) by 0.0300 inches relative to a nominal lug location.

Specifically, in this example, suppose that left/right lugs of an aircraft are misaligned by 0.0044 inches in an x-direction (e.g., forward/aft direction) and misaligned by 0.0130 inches in a z-direction (e.g., vertical direction). Since the eccentric boltmay be configured, as earlier described, to engage/contact the lug bearing prior to engaging the clevis surfaces, the eccentric boltis able to rotate (e.g., to take out misalignment in the x-direction) while the pod is adjusted slightly up and down (e.g., to take out misalignment in the z-direction) until alignment is made.

shows that there are two possible alignment positions to compensate for the misalignment and enable the joint to react loads in multiple directions (e.g., x-z directions) perpendicular to the axial direction (e.g., y-direction) of the eccentric bolt. In a first alignment solution, the pod is raised 0.0167 inches (i.e., 0.0297 inches−0.0130 inches=0.0167 inches). In a second alignment solution, the pod is lowered 0.0427 inches (i.e., 0.0297 inches+0.0130 inches=0.0427 inches). In either case, the alignment is achieved by rotating the eccentric bolta corresponding amount and the overall height change of one corner of the pod (e.g., length of pod may be approximately 20 feet) is not significant. Thus, to compensate for misalignment in this case, the pod may either by raised 0.0167 inches or lowered 0.0426 inches and the tapered ramps of the eccentric boltaid in starting the eccentric boltfor installing to the joint quickly, securely, and without drilling.

Although specific embodiments are described herein, the scope of the disclosure is not limited to those specific embodiments. The scope of the disclosure is defined by the following claims and any equivalents thereof.